s3X-raydiffractionMotivation:.X-ray diffraction is used to obtain structurainformation about crystalline solids· Useful in biochemistry to solve the 3Dstructures of complex biomolecules·Bridge the gaps between physics, chemistryand biology.X-ray diffraction is important for: Solid-state physics·Biophysics·Medical physics·Chemistry and Biochemistry
Motivation: •X-ray diffraction is used to obtain structural information about crystalline solids. •Useful in biochemistry to solve the 3D structures of complex biomolecules. •Bridge the gaps between physics, chemistry, and biology. X-ray diffraction is important for: • Solid-state physics • Biophysics • Medical physics • Chemistry and Biochemistry §3 X-ray diffraction
History of X-Ray Diffraction1895X-rays discovered byRoentgen1914First diffraction pattern of acrystal made by Knipping andvon Laue1915Theory to determine crystalstructure from diffractionpattern developed by Bragg1953DNA structure solved byWatson and CrickNowDiffraction improved bycomputer technology; methodsusedto determine atomicstructures and in medicalapplicationsThe first X-ray
History of X-Ray Diffraction 1895 X-rays discovered by Roentgen 1914 First diffraction pattern of a crystal made by Knipping and von Laue 1915 Theory to determine crystal structure from diffraction pattern developed by Bragg. 1953 DNA structure solved by Watson and Crick Now Diffraction improved by computer technology; methods used to determine atomic structures and in medical applications The first X-ray
HowDiffraction WorksWave lnteracting with a Single ParticleIncident beams scattered uniformly inall directionsWave Interacting with a SolidCrystalline MaterialRegular pattern of crystalline atomsproduces regular diffraction pattern.Diffraction pattern gives information oncrystalstructureNacl
How Diffraction Works Wave Interacting with a Single Particle Incident beams scattered uniformly in all directions Wave Interacting with a Solid Crystalline Material Regular pattern of crystalline atoms produces regular diffraction pattern. Diffraction pattern gives information on crystal structure NaCl
How Diffraction Works: SchematicX-Ray DiffractionX-rayTubeHighVoltageCrystalX-rayOBeamLead ScreenPhotographicPlate
How Diffraction Works: Schematic NaCl
How Diffraction Works: SchematicX-RayDiffractionX-rayTubeHighVoltageCrystalX-rayOBeamLeadScreenPhotographicPlate
NaCl How Diffraction Works: Schematic
How Diffraction Works: Bragg's LawX-rays ofwavelengthlQQQSimilar principleto multiple slit experiments Constructive and destructive interference patternsdepend on lattice spacing and wavelength of radiationBy varying wavelength and observing diffractionpatterns, information about lattice spacing is obtained
nl=2dsin(Q) • Similar principle to multiple slit experiments • Constructive and destructive interference patterns depend on lattice spacing and wavelength of radiation • By varying wavelength and observing diffraction patterns, information about lattice spacing is obtained How Diffraction Works: Bragg’s Law d Q Q Q X-rays of wavelength l l
DestructiveConstructiveInterferenceInterferenceED(hkl)(hkl)(hkl)
X-ray sourceX-ray detectorIncidentX-raysReflectedX-raysA0ed-BDCdsinedsineDifference inpath length =BC+ CDBC = CD = dhk/SinOnkDifference in path length = 2dnkisinonklMustbeanintegral numberofWavelengths, n = 2dhk/sinehkl(n = 1, 2, 3, ...)入 = 2dhkisineBragg Equation
x-raydetectormonochromator20-Hcrystal(being rotatedinto diffr. conditions)x-raysfrom generator
(111)1002=0.1542 nm (CuK-radiation)80(see)60(200)40(311)(220)20(222)(331) (420)(400)0502030406070809010011012020 (degrees)